A typical computer system includes at least a microprocessor and some form of memory. The microprocessor has, among other components, arithmetic, logic, and control circuitry that interpret and execute instructions necessary for the operation and use of the computer system. FIG. 1 shows a typical computer system (10) having a microprocessor (12), memory (14), integrated circuits (16) that have various functionalities, and communication paths (18), i.e., buses and wires, that are necessary for the transfer of data among the aforementioned components in the computer system (10).
An integrated circuit, such as the ones shown in FIG. 1, is electrically connected to a circuit board via a chip package. A chip package, which houses semiconductor devices in strong, thermally stable, hermetically sealed environments, provides a semiconductor device, e.g., the integrated circuit, with electrical connectivity to circuitry external to the semiconductor device. FIG. 2 shows one prior art type of chip package assembly that involves wire bond connections. The wire bonding process involves mounting a integrated circuit (30) to a substrate (32) with its inactive backside (34) down. Wires (not shown) are then bonded between an active side (36) of the integrated circuit (30) and the chip package (not shown).
FIG. 3 shows a more recently developed type of chip package assembly known as “flip-chip” packaging. In flip-chip package technology, an integrated circuit (40) is mounted onto a chip package (42), where the active side of the integrated circuit (40) is electrically interfaced to the chip package (42). Specifically, the integrated circuit (40) has bumps (44) on bond pads (not shown and also known and referred to as “landing pads”) formed on an active side (46) of the integrated circuit (40), where the bumps (44) are used as electrical and mechanical connectors. The integrated circuit (40) is inverted and bonded to chip package (42) by means of the bumps (44). Various materials, such as conductive polymers and metals (referred to as “solder bumps”), are commonly used to form the bumps (44) on the integrated circuit (40).
As discussed above with reference to FIG. 3, the bumps (44) on the integrated circuit (40) serve as electrical pathways between the components within the integrated circuit (40) and the chip package (42). Within the integrated circuit (40) itself, an arrangement of conductive pathways and metal layers form a means by which elements in the integrated circuit (40) operatively connect to the bumps (44) on the outside of the integrated circuit (40). To this end, FIG. 4a shows a side view of the integrated circuit (40). The integrated circuit (40) has several metal layers, M1-M8, surrounded by some dielectric material (48), e.g., silicon dioxide. The metal layers, M1-M8, are connected to each other by conductive pathways (50) known as “vias.” Vias (50) are essentially holes within the dielectric material (48) that have been doped with metal ions.
Circuitry (not shown) embedded on a substrate of the integrated circuit (40) transmit and receive signals via the metal layers, M1-M8, and the vias (50). Signals that need to be transmitted/received to/from components external to the integrated circuit (40) are propagated through the metal layers, M1-M8, and vias (50) to the top metal layer, M8. The top metal layer, M8, then transmits/receives signals and power to/from the bumps (44) located on the active side of the integrated circuit (40).
FIG. 4b shows a top view of the integrated circuit (40) shown in FIG. 4a. The top metal layer, M8, as shown in FIG. 4b, has a number of parallel regions. These parallel regions alternate between regions connected to VDD and regions connected to VSS. Such a configuration helps reduce electromagnetic interference. The top metal layer, M8, is configured such that it is orthogonal with the metal layer below, M7, as shown in FIG. 4b. Further, bumps (44) on the top metal layer, M8, are arranged in a non-uniform fashion with some areas of the top metal layer, M8, having larger numbers of bumps (44) than other areas.